1. Field of the Invention
Aspects of the present invention relate to a signaling method between a cognitive radio (CR) base station and a CR terminal in a CR environment, and a channel division method which is used for the signaling method, and more particularly, to a signaling method between a CR base station and a CR terminal, which can solve a communication error between the CR base station and the CR terminal, caused by interference of an incumbent system, and also solve an interference, which may affect a user of the incumbent system, when the CR base station does not recognize the incumbent system in a CR environment, and a channel division method used for the signaling method.
2. Description of the Related Art
A cognitive radio (CR) technology adjusts a frequency usage band of an operating system according to a neighboring environment. In this instance, examples of the CR technology include policies and technical methods which can intelligently utilize a frequency, such as a frequency detection and dynamic frequency change, a Detection and Avoidance (DAA) with respect to an allowed system and coexistence, a DAA with an identical CR system and coexistence, and the like. To effectively utilize limited frequency resources via publicly available frequency resources, a new technical requirement is necessary for existing wireless communication systems. However, a communication system, which utilizes a CR technology, must have a sensing ability, a cognitive ability, and an adaptability with respect to resources.
An Institute of Electrical and Electronics Engineers (IEEE) 802.22 Wireless Regional Area Network (WRAN) Working Group is preparing a standard with respect to a physical (PHY) and Media Access Control (MAC) layer interface. The interface enables a non-allowed system to utilize a spectrum, which is assigned to a television (TV) broadcasting service, based on the CR technology. To coexist with an incumbent system and avoid an interference, which may affect existing services such as a TV broadcast, a wireless microphone, and the like, a MAC protocol of IEEE 802.22 enables a CR base station to dynamically change a channel currently in use, or a power of a CR terminal when a usage of a spectrum, used by the incumbent system, is detected.
Hereinafter, an example of a hidden incumbent system in a CR environment will be described with reference to FIG. 1.
FIG. 1 is a diagram illustrating a hidden incumbent system in a CR environment according to the conventional art. In FIG. 1, a CR base station 100 provides a service to CR terminals 101, 102, and 103 by using a channel x. An incumbent system 104 may start the service for incumbent terminals 106 and 107 by using the channel x. The incumbent system 104 illustrated in FIG. 1 is, for example, a sky wave TV system. In the case of the incumbent system 104, a service time schedule is generally fixed. However, a communication service, such as breaking news, and the like, may be provided in an unscheduled time zone. Therefore, since the CR base station 100 is located in an area out of a signal range of the incumbent system 104, the CR base station 100 may not recognize the existence of the incumbent system 104. Thus, the CR base station 100 continuously provides a service to the CR terminals 101, 102, and 103 using the channel x. Also, since the incumbent terminal 107 is located in an area where signals of the CR base station 100 and the incumbent system 104 are overlapping, the incumbent system 107 is affected by an interference due to the CR base station 100. The CR terminal 102 is also located in the overlapping area, and thus may not inform the CR base station 100 of a channel occupation status of the incumbent system 104 due to a strong signal of the incumbent system 104. In this circumstance, the CR base station 100 may not recognize the incumbent system 104 and the incumbent system 104 is called a hidden incumbent system.
As illustrated in FIG. 1, a method in which the CR terminals 101, 102, and 103 may transmit sensed channel information and information about an interference channel to the CR base station 100, to stop the CR base station 100 from providing a service to the CR terminals 101, 102, and 103 via a certain channel which is being used by the incumbent system 104, is required.